Means for dust extraction and ventilation of grinding wheels



Sept. 25, 1956 w. H. WHITE 2,763,972 MEANS FOR DUST EXTRACTION ANDVENTILATION OF GRINDING WHEELS Filed March 13, 1953 3 Sheets-Sheet lINVE N TOR Wm M Houamq/v Wwrr Z; ATTORNEY Sept. 25, 1956 w. H. WHITE2,763,972

MEANS FOR DUST EXTRACTION AND VENTILATION OF GRINDING WHEELS Filed March1;, 1955 3 Sheets-Sheet INVENTOI? W/L L m /7 Ha LO RA N WH/TE i ATTORNEv 5M 1956 w. H. WHITE {763,972

MEANS FOR DUST EXTRACTION AND VENTILATION OF GRINDING WHEELS Filed March13, 1953 3 Sheets-Sheet 3 IIVI/ENTOR WALL/AM? Mama/WW www.13-

@Lii ATTORNE v United States Patent MEANS FOR DUST EXTRACTION AND VENTI-LATION F GRINDING WHEELS 'William Holloran White, Redditch, Birmingham,England, assignor to The British Cast Iron Research Association,Alvechurch, Birmingham, England "This invention relates to improvedgrinders and more particularly to means for dust control in suchmachines.

In existing systems of dust control the greater portion of the grindingwheel is enclosed, where the grinder is of the pedestal type, partly ina cowl and partly in a collecting box upon which the cowl is mounted andthrough which the dust-laden air is drawn bv an extraction fan. Evenwhen large volumes of air are rapidly drawn through the box or cowl inthis way, however, the efficiency of dust extraction is notsatisfactory, since the system fails to control the dust-ladenair-streams generated by the revolution of the wheel and discharged athigh velocity from the space between the top of the wheel and the cowl,and particularly the dust-laden air stream which moves with highvelocity over the top of the work and up the operators body into hisbreathing zone.

The improved system of the present invention comprises dust controllingand collecting means enclosing the grinding wheel, except for asuflicient working surface, to a maximum of the wear down mark on thewheel. Surrounding the exposed portion of the wheel, i. e. across thetop close to the wheel where it emerges from the cowl and vertically oneach side close to the sides of the wheel,

;there are provided slot openings to a plurality of ducts through whichhigh-velocity, low-volume streams of air are drawn by means of a fan orfans connected to or :situated in the ducts. In this way the exposedportion of 1the wheel is enclosed between curtains of rapidly moving airwhich are not penetrated by (i. e. are clear of) the currents ofdust-laden air from the wheel and the grinding action. if desired, meansmay be provided whereby the direction in which the slot openings facecan be varied, e. g. by rotation of appropriate portions of the ductsthrough a small angle, to suit the work in hand.

An independent extraction duct may withdrawn dustladen air from in frontof the work rest, the duct being for example expanded into a hopperplaced immediately in front of the work rest. This duct may, if desired,be carried through the lower portion of the collecting box, whilstremaining independent thereof.

An important feature of the invention is the provision of means, such asgenerally described hereinabove, for creating a curtain or curtains ofmoving air between the wheel and the breathing zone of the operator, thespeed of the moving air being sufficient to intercept any dust cloudsmoving in the direction of the breathing zone. It will be apparent thatthis can effectively be achieved by creating a more or less horizontalcurtain of moving air at a level somewhat above the level at which thewheel emerges from its cover (and hence well below the breathing Zone).The creation of a pair of vertical curtains, one on each side of thewheel, is of advantage in conjunction with the horizontal curtain.

The uppermost duct which produces the horizontal curtain of air abovethe wheel may be divided to form two or more divergent sub-branches,with slots facing inwardly, which, with a breast-piece connecting theirIf desired, the breast-piece an inwardly facing slot. 7

drawn through the collecting two ends form a triangle. may also beprovided with Optionally air may be box and hood.

It is of advantage that the collecting box should be of large volume andin the preferred form of the inventic-n it is large enough to containone or more grinding wheels and the driving mechanism suitably mountedand enclosed. It may indeed be a large chamber through a slot or slotsin the front wall of which suficient working surface of the grindingwheel or wheels protrude, suitable work rests being provided. In .such aconstruction the upper part of the chamber takes the place of the cowlor cowls. The large volume ensures that the air in the chamber orcollecting box shall be relatively quiescent so that the dust cansettle. An outlet pipe at the back of the chamber or box may beconnected to a chimney and/or may contain an exhaust fan.

In all forms of the invention the work rest is preferably slotted orperforated, and may be seated on a suitable extension of the collectingbox.

Some embodiments of the invention will now be described with referenceto the accompanying drawings, in which:

Fig. 1 shows in perspective a pedestal grinder provided with means forcreating curtains of high-velocity air between the grinding wheel andthe operator.

Fig. 2 shows a variant in which a breast piece is provided.

Fig. 3 shows in perspective a two-wheel grinding unit provided withmeans for creating air curtains as in Figures l and 2, but housed in alarge collecting box or chamber.

Fig. 1 shows a grinding wheel 1 partly enclosed in a cowl 2 over acollecting box 3 through which passes a lower exhaust duct 4, ending ina hopper 5 extending the full width of the collecting box 3 and from thefront of the latter to the work-rest 6. An upper exhaust duct 7 isprovided with two side-branches, 8, 9, having vertical slots 10, 11. Theupper duct 7 also serves a pair of horizontal sub-branches 12, 13,provided with slotsl4, 15. As shown diagrammatically, ducts 4 and 7 areboth connected to the intake of a single exhaust fan indicated at F.

In Fig. 2, in which corresponding parts bear the same numbers as in Fig.1, the upper duct serves two subbranches 16, 17, provided with slots 18,19 on their inner faces, and joined at their ends by a breast piece 20,some 8 inches in front of the grinding surface of the wheel 1. Thebreast piece 20 will usually be concave when viewed from the operatorsposition. In the particular arrangement shown, each of ducts 4 and 7 isconnected to a separate exhaust fan F.

In each case it is convenient to have flexible connecting tubes 21, 22to connect the vertical pieces 8, 9 to the branch pipes of the duct 7;this permits of the adjustment of the sub-branches (12, 13 in Fig. l;16, 17 in Fig. 2) to any desired angle with the horizontal.

Fig. 3 shows a pair of grinding wheels 31, 31, mounted on a countershaft32 rotated by an electric motor 33. The whole, exceptfor a suflicientportion of the wheels for working purposes, is enclosed in a largeexhaust chamber 34 provided with an exit pipe 35 which contains anexhaust fan 36 (or is connected to a suitable chimney) for themaintenance of reduced pressure in the chamber 34. The work rests 37, 37are supported on extensions 38, 38 of the exhaust chamber 34 whichencloses lower portions of the wheels 31, 31, without, however,approaching them closely. Close to each wheel where it emerges from thechamber 34 is an air-extracting duct 39 provided with a fan 40 andopening into the chamber 34. The rear opening of the duct 39 directs ahigh-velocl 3 ity, low-volume stream of air towards the periphery of thewhen 31 within the crnainiber 34. The "front portion of duct 39 lyingoutside the chamber '34 carries a slotshaped nozzle 41 rather longerthanthe thickness of the wheel 31, and is provided with two branches '43disposed yertically'on either side of the wheel 31. These branches "43have slot-shaped lengthwise openings 44 which create side curtains ofhigh-velocity, low-volume air-streams, whilst a similar horizontalair-stream created by nozzle 41 completes the protection of theoperator.

If desired, ducts with funnel inlets, situated similarly to duct linFigs. 1 and 2, may be added to the unit shown in Fig. 3. Such ducts maybe provided with exhaust fans and/ or maylead into the exhaust chamber34. 'A'fsingleexhaust chamber of sudicient'sizecan serve for any desirednumber of grinding uni-ts. It may be external to the grinding roomitself, with one wall in cornmonprovided with panelswhich can bereplaced with 2-'wheel grinding units as required. Each unit may haveits owndriving' motor, or may be driven by belting from a common shaftwithin the chamber.

In all forms'of the invention described a high-velocity air curtain iscreated between the dust'generation point and'the breathing levelof theoperator, and ihthe form of the invention illustratedin Fig. 2 the bodyof the operator, pressed againstthe breast-piece Zih'effectively sealsoff the dust-contaminated area.

In operation the heavy dustis thrown by the'a'cticn of thewhe'el and theperipheral air streams into the collectingbbx'where thevelocityfd'ecreases and allows the dust to settlejby"'gravitat-ion, andthe light air-borne dust is ollected'by the system of extraction aircurtains. As is evident, the separate air-exhausting system which'provides these air curtains is isolated on the low pressure side fromthesp'ace within the enclosing means (e. g. cowl) by which the wheel issurrounded.

I claim:

' 1. In combination a grinding wheel housed, except for a sufiicien-tworking portion, in a relatively large chamber, means for maintainingthe air in the chamber at less than atmospheric pressure, a work rest,means for withdrawing dust-laden air from the vicinity of the work rest,and a plurality 'of air-extracting duets with slot-shaped intakeopenings so disposed as to create curtains of high-velocity, lowvolumeair currents above and on each side of the exposed portion of the wheel,the said'ducts being arranged to discharge the dust-laden air into thesaid chamber.- I V p Incombination a grinding wheel housed, except fora'sufficientworking portion, in a relatively large chamber, means formaintaining the air in the chamber at less than atmospheric pressure, awork rest, means for withdrawing:dust-laden air from the vicinity of thework rest, and a plurality ofYair-extracting ducts with slotshape'dintake openings so disposed as to' create curtains of"hi'gh-velocity,low-volume air currentsabove andon each side of the exposed portioniofthe wheel, the said ducts being arranged to discharge the dust-laden airinto the said chamber in-the-"dire'c'tion of the unexposed portion ofthe Wheel 7 3; In combination, a grinding wheebmounted upon a collectingbox' and otherwise surrounded,;'except' for"a sufiic'ient workingsurface, by a cowl, a work res-t, means for withdrawingdust-laden airfrom the vicinity of the 'work rest through said cowl and aplurality ofair-extract- 'ing ducts isolated from the space within'th'ecowl and each'h-aving a"slot shaped intakeope'ning, at least one of said openingsbeing disposed horizontally and sufficiently above/the pointwhere thewheel emerges from the cowl to be clear'of'the highvelo'city layer ofair carried round the wheel while-at least two others of said openingsare disposed vertically one on each side-of the exposed part of-thewheel periphery so as to create,-respectively,

at least one substantially horizontal curtain of high-veloc- .ity'low-volume air cu'rrent'at a short distance above the level at which thewheel emerges from its cover, and a "suistannany vertical similar"curtain 'on each side of the emergent wheel.

4. In combination a grinding wheel mounted upon a collecting box andotherwise surrounded, except for a sufficient working surface, b'yacowl, a work rest, a high speed air stream generator, and a plurality 0fextraction ducts extending from the low pressure side of the saidgenerator and each terminating in a slot-shaped opening located clearerthe layer of high speed air-carried round by the wheel and so "disposedas to create at least one substantially horizontal curtain bfhigh-velocity, low volume 'air cur'rent at a short distance abovethe'level at which the wheel emerges from its cowl, and a substan-'tially verti'cal'similar curtain on each side ofthe emergent wheel, thedust-laden air drawn through the ducts being discharged behind theemergent portion of the wheel.

5. A pedestal grinder comprising a casing, a grinding wheel'lbc ated inthe top 'of' said casing, an opening in "the front wall 'of's'aid casingthrough which a portion of the periphery 'ofs'aid wheel protrudes,a'worlc rest locatedad jaeentthe' exposed portienof the wheel periphery,a high speed air flowgenerator isolated, on at least itslow'pressur'e'side, from the space within the casing, and ductingleading from thesaid low pressure side of the generator to firstelongated dust intakeepening'in'front of and below the work rest asecond elongated dust intake OpeningeXtending parallel to thewhecl axisand located adjacent the point cfemergence of the wheel from the casing"but clear of'the layer of high velocity air carried round"by the'whcel,saidsecond intake opening serving to create'a hfgh'veiocity' low volumecurtain of airbetween the operator and the'wheel.

6. in combination, a suitably mounted'grinding wheel sur'i'eun'ded,except "for a suihcient working surface, by apprepriate'enclosingmeans,an air-exhausting system 'Cbmprisihg-aduct on the lowpressure side ofsaid system isolated from the space within said enclosing means, Said"duct having at least one elongated air intake opening disposed generallyhorizontally a short distance above the uppermost part'of said workingsurface of the wheel, and means for withdrawing air through said intakeopening to establisha high-velocitylaw-volume curtain ofair ex-'-ternally-of said enc'losingrneans between the eperators rea'thingfzone and said 'whecl and clear of the layer-0f h'i'gh 'yelccity air'carried round by the wheel.

5 7&Thect3mbination set fcrth'in claim 6 wherein said air-exhaust"system"ttir'ther'includes ducts isolated from the spacawithin saidenclosing means on either side of the' exposed partof the Wheel havingelongated air intake openings disposed substantially vertically so as tocreate a substantially veitical'curtain of high-velocity low-volnineair-current oneach side of the exposed part of the wheel.

'j-8.--The *eoii1bi1iatibn set forth in claim 6 which furtherihclud'esseparate means" for witl'idrawing dust-laden air from alocation adjac'ent said working surface.

9. The combination set forth in claim 6 which further includes a 'w'orlcrest and separate means for withdrawing dust-laden air-frem thevicinityof said work rest, said "exhaust duiztcomprising a'pairof convergentelongated air' intakememb'ers extending from the position of the I=operators' body to a point above the point-ofemergence of the wheelf-rcm'its enclosing means.

10. The method of dust extractionfor grinders'which comprises theestablishment, between the exposed port-ion-of 'the'wheel periphery andthe breathing zone of the operator, of a fast-moving low-volume aircurtain having a lateral spread suflicient to trap particles of dustmoving upwards between the operatorsbody andthe wheel, and physicallyisolated throughout its low pressure circuit from the chamber withinwhich the shielded. part of the wheel is located.

lIJ'The'methOd of dust extraction for grinders which i comprisesestablishing; in the space between the exposed portion-of the'wheelperiphery and'the operatorsbe'dy,

at least three high-velocity low-volume air curtains, each moving fromthe operator towards the wheel and each physically isolated throughoutthe low pressure portion of the total flow circuit from the chamber inwhich the shielded part of the wheel is housed, one of said curtainsbeing established in a plane tangential to the wheel periphery andtransversely between the wheel and the breathing zone of the operator,While two other curtains are established in generally vertical planesone on each side of the exposed portion of the wheel and of a height, 10

at the intake aperture, approximately equal to the height of the exposedportion of the wheel above the work-rest.

References Cited in the file of this patent UNITED STATES PATENTS673,047 Dennis et a1 Apr. 30, 1901 6 Middleton Apr. 11, 1905 Mueller May20, 1913 Power July 8, 1919 Segui June 6, 1933 McElevey Dec. 17, 1940Bagshaw Oct. 7, 1941 Walpole Apr. 13, 1943 Harrison Mar. 7, 1950 FOREIGNPATENTS Italy Oct. 29, 1936 Great Britain Aug. 1, 1940

